Folding door is a type of door that opens by folding back its panels in a concertina-like manner. Also known as accordion doors or bi-fold doors, they consist of multiple hinged panels that fold onto each other when the door is opened. This design allows for a wide opening while taking up minimal space when the door is fully open. Folding doors are commonly used for closets, room dividers, patio entrances, and other spaces where a large, unobstructed opening is desired.